Calipers.



No. 745,229. PATENTE D NOV. 24, 1903. W. A. MCDONALD.

OALIPERS. APPLICATION FILED JULY 13,1903.

N0 MODEL.

ATTORNEYS WITNESSES L UNITED STATES iatented November 24, 1903.

PATENT OFFICE.

CALIPERS.

SPECIFICATION forming part of Letters Patent No. 745,229, dated November24, 1903.

Application filed July 13, 1903. Serial No. 165,223. (No model.)

To all whom it may concern:

Be it kn own that I,WILLIAM A. MCDONALD, a citizen of the United States,residingat Garfield, inthe county of Bergen and State of New Jersey,have invented certain new and useful Improvements in Calipers, of whichthe following is a specification, such as will enable those skilled inthe art to which it appertains to make and use the same.

My invention relates to improvements in calipers and comprises two armspivotally connected, one of which arms is provided with a secondaryswinging arm and a lever to operate an index-hand to indicate upon ascale the gage or size of the opening between the adjacent points of thecaliper-arms.

The object of my invention is to provide a caliper of the characterdescribed which will readily indicate upon a scale formed upon thecaliper the size of the opening between the ends of the caliper arms orgage of the object measured.

The invention is fully disclosed in the following specification, ofwhich the accompanying drawings form apart, in which the separate partsof my improvement are designated by suitable reference characters ineach of the Views, and in which- Figure 1 is a side view of my improvedcalipers; Fig. 2, a similar view which shows the ends of the armsseparated and measuring an object; Fig. 3, an enlarged end view of Fig.1 looking in the direction indicated by the arrow at. Fig. i is a detailview of a part of the device detached.

In the practice of my invention I provide the arms a and b, which areheld together at c, and upon the arm a I form an extension 0. which witha portion of the said arm forms a scale which is suitably marked withgraduations (L The arm a, terminates at g, and at this point I pivotallyattach a finger b the upper end of which is adapted to engage the end bof an index-hand b pivotally attached to the arm a. The lower end of thefinger b is formed with a recess ,which engages a pin (1, which isfastened to the secondary arm (2. This secondary arm e is pivotallyattached to the arm a at c and is provided with a stop a which engagesthe back of the arm a, as clearly illustrated in Fig. 3. To

keep the finger b normally in its outermost Patent, is--.

position, I employ a spring 12 which is socured to the finger at b andengages a pin 5 which is fastened to the arm a. The in deX-hand b isheld upon the arm a by means of a screw or pinf, and engaging betweenthe head of the set-screw and index-hand b I provide a spring f which isadapted to keep the said index-hand flat against the face of the scale;

In the operation of my device when it is de sired to find the gage orthickness of wire or other material the said material is forced betweenthe ends of the arm I) and the secondary arm 6, thereby forcing the saidsecondary arm eoutward, and actuating the finger 1) moves the index-hand6 until it indicates upon the scale the thickness of the materialmeasured in the proper way. When the object measured has been removedfrom the ends of the arms 17 and e, the action of the spring b willbring the ends of the arms band 6 together to their normal position, asshown in Fig. 1.

This device is simple in construction and operation and comparativelyinexpensive, and various changes in and modifications of theconstruction herein described may be made without departing from thespirit of myinvention'or sacrificing its advantages.

Having fully described my invention, what I claim as new, and desire tosecure by Letters 1. In a caliper, two arms attached at one end, one ofwhich is provided with a scale, a

secondary arm pivotally connected to one of the arms, an index-handattached to said arm and operating in conjunction with said scale, aleverpivotally attached to the said arm and adapted to operate the saidindeX-hand,means for operating the said lever in conjunction with thesaid pivotal arm and means for keeping the ends of one ofthe arms andthe secondary pivoted arm normally together, substantially as shown anddescribed.

2. In. a caliper, two arms attached at one end, one of which is providedwith a scale, a secondary arm pivotally connected to one of the arms, anindex-hand attached to said arm and operating in conjunction with saidscale, a lever pivotally attached to the said arm and adapted to operatethe said index-hand, a pin formed upon the said secondary arm andadapted to engage in a slot formation upon the end of the said lever toactuate the same during the movement of said secondary arm,

- substantially as shown and described.

3. In a caliper, two arms attached at one end, one of which is providedwith a scale, a secondary arm pivotally connected to one of the arms, anindex-hand attached to said arm and operating in conjunction with saidscale, a lever pivotally attached to the said arm and adapted to operatethe said index-hand, a pin formed upon the said secondary arm andadapted to engage in a slot formation upon the ends of the said lever toactuate the same during the movement of said secondary arm, 15

